1. Field of the Invention
The present invention relates to a spatial optical modulator, more specifically to a temperature adaptive optical modulator.
2. Background Art
Today's development of display technologies has increased the demands for realizing large-sized images. Most of the large-sized image display apparatuses (e.g. a projector) are currently using liquid crystal as optical switches. Liquid crystal projectors are more popular than conventional CRT projectors, due to their compact sizes, low prices and simpler optical systems. However, when light emitted from a light source passes through a liquid crystal film and is displayed on a screen, a lot of optical losses occur in the liquid crystal projector. Accordingly, a method for reducing the optical loss has been developed to display an image more brightly by employing a micro-machine such as a spatial optical modulator using reflection.
The micro-machine refers to a machine that is too small for a naked eye to be identified. This micro-machine can be referred to as a micro electro mechanical system (MEMS) or a micro electro mechanical device, which is created by applying semiconductor manufacturing technologies. The MEMS is applied for a lot of information apparatus elements, such as a magnetic head and an optical head, by using a micro optical device and an extreme device. The MEMS is also applied in the field of biomedicine and semiconductor manufacturing processes by using a variety of microfluidics. The micro-machine can be grouped into a micro sensor, functioning as a sensing device, a micro actuator, functioning as a driving device, and a miniature machine, transferring other types of energy.
The MEMS, which is one of various application fields, is being used for optical science. If the MEMS technologies is used, not only optical devices having a smaller size than 1 mm can be manufactured but also micro optical systems can be realized by using the optical devices.
Micro optical elements, such as optical modulators and micro lenses, which belong to the micro optical system, are employed and applied in communication apparatuses, displays and recording apparatuses, owing to their quick response, little loss, and easy integration and digital capabilities.
A spatial optical modulator (SOM), which is used for a scanning display apparatus, a type of display, is configured to include a driving integrated circuit and a plurality of micro-mirrors. At least one micro-mirror is used, to thereby represent a pixel of a projected image.
At this time, in order to represent light intensity of one pixel, the micro-mirror changes the quantity of modulated light by adjusting its displacement according to a driving voltage supplied from a driver IC. Here, the driver IC generates a driving voltage having particular relationship with an input signal.
However, the spatial optical modulator has its proper efficiency in a certain temperature environment. Particularly, in case that driving means driving the micro-mirror use a piezoelectric element, the spatial optical modulator has great efficiency in reflecting and diffracting an incident beam of light at a temperature of approximately 80 degrees Celsius. This is because the distance between the micro-mirrors can be sensitively varied depending on the temperature. Accordingly, it becomes necessary to develop a temperature adaptive optical modulator that can be operated efficiently even though a display apparatus is in an improper temperature environment.